1. Field of the Invention
This invention relates to rotary diaphragm positive displacement pumps.
2. Background Prior Art
A typical rotary diaphragm pump consists of a rigid tubular housing with an annular channel running around the inner surface, which acts as the pumping chamber, and a flexible tubular diaphragm which is caused to orbit eccentrically in the channel thereby sweeping the fluid in its path from the inlet port to the outlet port. These ports are usually separated by some form of active partition which can form part of the diaphragm moulding and which is caused to be elastic by one of a number of different means.
This type of pump has a wide range of fluid pumping applications. The main benefits are that it does not rely on close fitting sliding components to develop a useful pressure and does not require shaft seals or valves, all of which are subject to wear and can cause pump failures.
Existing rotary diaphragm pump designs aim to provide higher pressures and operating speeds and lower levels of friction and wear but this in turn has led to an increase in problems associated with a pulsating input and output such as cavitation, water hammer and general noise. Pulsations can damage delicate fluids such as carbonated beverages and can cause over-rapid operation of pressure sensitive switches, plunger bounce in solenoid valves, and other system problems.
Existing designs also suffer from a lack of support for the diaphragm where it is at its furthest point from the housing wall. This renders the diaphragm vulnerable to early failure.